Modified Asphalt with Graphene-Enhanced Polymeric Compound: A Case Study

Round 1

Reviewer 1 Report

The main objective of the review is to upgrade the current knowledge on bituminous mixture fatigue behaviour reinforced with graphene.

This topic was developed using a very complete research methodology.

The introduction is well written and easy to understand. The bibliographic research is complete and well analyzed.

The paper is inspired from both of the theoretical and methodological point of view. Aims and methods are clearly described and supported with sufficient theoretical background.

Another positive aspect of the work is the variety of bituminous mixture analysed. This variety allowed to have a multidimensional interpretation of the performance of different modifed bituminous mixtures both on site and in laboratory.

Pag.5 line 156-160

It’s better to describe the different “unit” in the first formula.

Pag.6 line 183

Probably "charcterized" stands for "characterized"

Pag. 7 line 232

Probably "Prove" stands for "Test"

Pag. 11 table 4 - first row

Probably "Larghezza media" stands for "Average width" 

Pag. 16 conclusions- line 415

It'd would be very useful to know some more data about the average traffic and Heavy traffic load that pass through the 4 sections during the experimental test.

It'd would be very interesting to have some more information about the minumum temperature during the winter and the average in a week higher temperature during summer together with some information about the number of rainy days.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

In this paper, four different kinds of modified asphalt concrete are compared and analyzed by laboratory and field tests. The study was designed to compare the performance of GPC-added AC with three other AC mixtures commonly used in road construction. The study evaluated the stiffness and fatigue behavior of materials at different temperatures through ITSM and ITF tests. The results showed that the GPC-modified AC exhibited the highest stiffness at medium and high temperatures and the best performance in terms of fatigue behavior. Besides, the addition of GPC significantly improved the material's resistance to permanent deformation at high temperatures. By surveying and calculating the PCI index, the study also assessed the extent of damage over the service life of the four sections. Among them, section S1, which uses the M1 mix, performed best when it is subjected to heavy traffic. Based on the FWD test results over six years, the study also evaluated the long-term performance of different AC mixtures. The results indicate that the S1 section using a GPC-modified AC mixture consistently exhibits high modulus over the six years, showing better structural integrity and deformation resistance than other mixtures. The elastic moduli of AC mixtures in the S2, S3, and S4 sections gradually decreased, inferring that structural failure was more likely to occur. The GPC-modified AC mixture is conducive to extending road surface life and maintaining structural integrity, especially under high traffic loads and different climatic conditions.

The paper is more like a project report. The conclusions obtained in the manuscript are easy to understand even without the tests and data analysis. The authors are suggested to further refine the research results, specify research problems with scientific value, and form corresponding supporting results. Besides, there are some comments that could help the authors improve the manuscript shown as follows.

l  Page 1 “Title”: The article was titled “Comparative Performance Evolution of Modified Asphalt Concrete: A Case Study”, but the main content of the manuscript is the study of GPC-modified asphalt concrete. Therefore, it is suggested to modify the title and specify the main topic of the manuscript.

l  Page 1 “Abstract”: More quantitative indicators can be added to the conclusion of the abstract, such as the comparison of the S1 modulus and other pavement structure moduli mentioned in the paper.

l  Page 2 “Introduction”: a paragraph introducing the sections and structure of the manuscript should be added at the end of the Introduction.

l  Page 3 “Materials and Methods”: The method part is lengthy. The basic introduction of the test methods which is known by the peers can be simplified, and a flow chart could be added to increase the readability of the manuscript.

l  Page 3 “Figure 2”: The abbreviations in the figure such as “M1w, M1h…” should be announced when used for the first time.

l  Page 4 “Figure 3”: The name of the y-axis should be “passing rate (%)”, and the label for the sub-figures should be consistent with that in the figure caption which is not “a) and b)” but “(a) and (b)”.

l  Page 11 Table 4: “larghezza media” is in Italian, the language used in the manuscript should be consistent.

l  Page 12 line 331: When calculating the density of distresses, the concept of the distress area was put forward. However, the specific calculation method of the distress area was not explained. Take the pavement cracking for example, the division of the distress and the disease-free area varies from person to person, which will lead to different distress area calculation results. Therefore, the authors are suggested to give a detailed description of the calculation method of the distress area.

l  Page 13 Table 6: According to the results shown in the table, S1 illustrated an obvious variation of PCI in different positions, can the authors explain the reason why and demonstrate the rationality of PCI calculation results for different test sections?

l  Page 14 “3.2.1. FWD results”: In this section, please explain in detail the reasons for conducting FWD tests on the foundation and subgrade.

l  Page 16 “4. Conclusions.”: The authors are recommended to refine the conclusions by reducing the process description and adding more quantitative data to important points in the conclusion.

Moderate editing of English language required.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

I find the submitted manuscript interesting and worth of publication, if the remarks presented below are addressed to.

Introduction - the list of tested additives is, obviously, not complete. The Authors should clarify, why they presented only a selected group of them.

Section 2 - please, provide the longitudinal profiles of the sections (S1-S4). Are the extreme slopes similar? This parameter (according to eg. German RStO) highly influences the expected exploitation period of the pavement structure.

Table 1 - clarify, if the percentage rerefrs to the mass or to the volume.

Formula 1 (line 159) - what is the difference between specimen and sample? "h" is supposed to be the height rather.

Line 176: Use the subscript in Epsilon_0. Strain is a dimensionless quantity. Please, describe in this context the "pseudo-unit" of micro strain.

Line 232 - is the word "prove" necessary herein?

Line 249 - "fine-tuned" is not a precise desription f the engineering procedure. In my opinion, this part should be extended. I have two main remarks at this level:

- how do you justify the simplification of the pavement structure behavior just to linear elasticity?

- using the back-calculation there is no unique solution. Using various combinations of layers' parameters one can obtain the same result (deflection field). Please, provide the methodology you use to select one combination.

Figure 6 - I am not convinced that behavior of ashalt layers at temperature of 40 degrees Celsius is still linear elastic...

Line 287 - it is rather unexpected to extrapolate the results in such a manner. The extrapolation period is too long.

Table 4 - use English descriptions only, please.

Figure 11 - comment on the back-calculation procedure.

Comment on the costs of each section (S1-S4).

I find English good, no serious mistakes detected.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The authors respond to the previous review comments.

 Minor editing of English language required.

Reviewer 3 Report

I find the revised version of the manuscript suitable for the publication in a scientific journal. It should be, however, noticed that the results are of preliminary character. Particularly, the method of back-calculation is presented in a form of a black-box method. The results cannot be reproduced, in fact. It reduces the scientific level of the research. I encourage the Authors to focus on this issue in their future research.

I find English correct. Only a small number of language isssues were corrected.